Safety device for elevators



Feb. 2, 1960 Filed Nov. 21, 1955 W. STELZER SAFETY DEVICE FOR ELEVATORS 2 Sheets-Sheet 1 United States SAFETY DEVICE FOR ELEVATORS William Stelzer, Summit, NJ. Application November 21, 1955, Serial No. 547,940 12 Claims. cr. 187-13) The invention relates to a safety device for elevators and more particularly to a device for adjusting to the required lifting force of the elevator car when the latter is started toascend and to break the electric circuit to stop the car when the weight or drag of the car is changed during its ascent or descent relative to what it was at the start.

The novel device is particularly adapted for use with inclined or stair elevators where the runway is open and damage by collision is easily possible.

The object of the invention is to provide a simple and inexpensive safety mechanism responsive to the tension in the tow line to interrupt the control circuit of the elevator and to thereby stop the car if the tension is changed a certain amount during the travel of the car. Another object is to place the control device remote from the elevator, car to reduce the number of electric leads to the moving elevator car. Another object is to provide a resiliently supported sheave for guiding the tow line which supports the elevator and to use the movement of the sheave in response to an increase or decrease in .the tension, of the tow line during operation of the elevator to control the electric circuit to stop the elevator.

A further object is to use the position of the resiliently supported sheave, which is indicative of the tension in the tow line, to interrupt the circuit and thereby cut the power when the tension is dangerously high or reduced as in the case of rupture of the tow line, and to cut out one part of the control circuit if a certain tension is exceeded above the tension caused by the unoccupied elevator car so that if the car is occupied it is not possible to operate the car except from the controls in the car itself.

Other objects and advantages of this invention will be apparent from the following description considered in connection with the accompanying drawing submitted for the purpose of illustration and not to define the scope of the invention, reference being had for that purpose to :the vsubjoined claims. In the drawings, wherein similar reference characters refer to similar parts throughout the several views:

Fig. 1 is a side elevation of the device incorporated in the track of an inclined elevator, only the upper end of .the track being shown and all enclosures or other elements not related to the safety device having been removed;

Fig. 2, a section taken on lines 2-2 of Fig. 1 showing mainly the sheave and support for the pulley, the electric switches having been removed in order not to encumber the drawing; r

Fig. 3, a diagrammatic sectional side view of the upper part of the inclined elevator to show the relation of the pulley, motor-driven drum, and elevator car;

Fig. 4, an electrical diagram of the'control and power circuit of the elevator;

Fig. 5, a view similar to Fig. 1 showing the position of elements when the elevator car is loaded;

Fig.6, a View similar to Fig. showing the position of Patented Feb. 2, 1960 2' elements after the load or resistance has been further increased during operation of the elevator;-and 1 Fig. 7, a fragmentary view similar to the lower portion of Fig. 6 illustrating the operationof the safety device when the load is reduced below that of the empty elevator car. i

Before explaining the present invention in detail it is to be understood that the invention is not limited in its application to the details of construction andarrangement of elements illustrated in the accompanying drawings, since the invention'is capable of other embodiments and of being practised or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not limitation.

The elements in Fig. 1 have been arranged somewhat diagrammatically in order to give a better illustration of the device. The latter is built into or under an inclined track whose main part consists of a plate 1 secured to the, structure of the building and also serving as the supporting framework or base for the ,various elements of the safety device. A pulley or sheave 2 revolves around a bearing stud 3 of an axle 4 having arms 5 pivotallySe cured to brackets 6 by means of pins 7. The brackets are secured to plate 1 and the pulley extends through the plate, the latter having a hole 8' niade for that purpose. A tow line 10 passes over pulley 2. This tow line, may] consist of a cable, wire, belt, chain, or the like, and has one end fastened to elevator car 11 and the otherto a drum 12 which is driven by an electric motor indicated in the diagram in Fig. 4 by numeral 14.

Pulley 2 and axle 4 are biased by tension springs 15 in a direction to resist the tension in tow line 10. The tension springs have a definite and positive rate of increase of force, i.e, their force increases as they are extended. If the' tow line passes over the 'pulley as shown, the force acting on the axis of pulley 2 is-alfrnost twice as great as the tension in tow line 10. Thus springs 15 must have considerable strength. If in constructing the device the distance between pins'7 and the axis or" pulley 2 is reduced or the angle between the two'ends of tow line 10 is increased, the force opposing springs 15 is reduced. This angle is given in most cases by the elevator construction, i.e., the location of drum 12 relative to the track or pulley 2. One end of each spring 15 is hooked to a lug 16 of axle 4 and the other to a bracket 17 rigidly secured to plate 1. A segmental arm 18 having an arcuate V-shaped groove 20 extends from axle 4 and cooperates with a bevel edged link 21 pivotally supported at one end by a link 22 hinged to plate 1 at 23, and at the other end by a double link 24 hinged to a pull type solenoid 25 at 26. The solenoid is secured to bracket 17 or plate 1. The groove 20 follows an arc struck from the center of pins 7. Arm 18 and link 21' together form a clutch, which is disengaged in 'the position shown where the elevator is at rest and motor 14- deenergized. A light leaf spring 27 secured to a cross member 28 of link 21 abuts against a tab 29 extending from bracket 1'7 and holds link 21 in a neutral position, as shown, the weight of link 21 not being sulficient to overcome leaf spring 27. Leaf spring 27. is preloaded to rest on cross member 28 when in the neutral position. A normally closed safety switch 30 mounted on a bracket 31 extending from plate 1 is so positioned that it is operated by link 21 when the latter is moved. It is desirable that switch 30 is opened by movement of link 21 in either direction away from the neutral position. For this purpose I provide a double-armed lever 32 fulcrumed at 32 to the housing of switch 30. One end of one arm is interposed between the end of link 21 and the operating button of switch 30, and the other end of lever 32 has a pivotally secured hook. 34 engaging groove 33 of link 22. A bracket 40 secured to plate 1 carries a pair of normally closed safety switches 41 and 42 and a normally open interlock switch 43 held closed by 'a leaf spring 44 when there is no load on elevator car '11. It is understood that a normally closed switch is of the type that is closed when external pressure on the operating button is released, and a normally open switch is biased to be open, closing only when external pressure is exerted on the button of the switch, such a'butt'on being indicated by numeral 62 in Fig. 5. Leaf spring 44 is secured to an arm 45 extending from and rigidly connected to axle 4. This leaf spring 44 permits an overtravel when axle 4 swings clockwise to the extreme position where arm 18 abuts against bracket 17 and arm 45 opens safety switch 41. The second safety switch 42 is so positioned that when axle 4 swings in a counterclockwise direction towards the extreme position where arm 18 abuts against bracket 40, it is opened. Link 21 carries a latch member 46 pivotally secured at 47 and cooperating with a catch 48 on bracket 17. In the position of axle 4 assumed when there is no load on car 11', latch 46 is held disengaged from catch 48 by a stop 49 welded to or otherwise secured to arm 18. The latch member may be made of a metal plate where one end 48' is bent out of the plane of the plate to meet and abut against stop 49.

Referring now to diagram shown in Fig. 4, illustrating the electrical connection when the elevator is at rest and the car empty, numeral 50 denotes the electric line, 51 is a conventional reversing relay having solenoids 52 and 53; 54 are bus bars running along the track for an electric connection to the up and down push buttons 55 and 56 located on the elevator car 11. When car 11 is empty and switch 43 therefore closed, the elevator may be operated by call push buttons 57 and 58 at the upper and lower landings, respectively. Conventional limit switches 60 and 61 are provided which are normally closed and are opened by the car when the end station is reached.

In the embodiment shown, power line 50 consists of three leads, such as are used with three phase current. Thus electric motor 14 is considered a three phase or squirrel cage motor, where reversal of any two leads reverses the direction of rotation of the rotor. One lead 65 from line 50 connects directly to motor 14, and the other two leads 66 and 67 connect to the switches 68 and 69, respectively, of reversing relay 51. These switches 68 and 6 9 are mechanically interlocked with solenoids 53 and 52. They can be in neutral as shown, Where motor 14 is deenergized, or if one of the solenoids 52 and 53 is energized one switch is connected to motor lead 70' and the other to 71. Motor leads 70 and 71 are tapped by wires 72 and 73 to energize solenoid 25. Lead 67 has a branch wire 74 having a series of switches 39, 41, and] 42 interposed and leading to the central bus bar of bus 54. The switches 30, 41, and 42 are of the normally closed type 'so that the central bar of bus 54 is energized unless one, of the switches is opened by a mechanical element of the device. Lead 74 where it connects to bus 54 branches out with a connection 75 to a switch 43 from where one wire 77 leads to solenoid 52 via call button switch 57 and limit switch 60; a second lead 78 leading from switch 43 via call button switch 58 and limit switch 61 to solenoid 53. Switch 43 is of the normally open type but is held closed by spring 44 whenever car 11 is empty. A return lead 89 from solehold 52 and 53 to lead 66 completes the circuit. Push button switches 55 and 56 are located on the elevator car. The latter has trolleys or brushes 81, 82, and 83 sliding on the bars of bus 54. The brush 82 connects with the central bar of bus 54 and has a lead 84 to energize one terminal of switches 55 and 56, the other terminal of each switch being connected by leads 85 and 86 to brushes 81 and 83, respectively. The upper bar of bus 54 is'connected by'a wire 87 to lead 77, and the lower 4 bar of bus 54 by a wire 88 to lead 78 leading to solenoid 53.

Describing now the operation, and assuming that the elevator is not loaded and at rest in the position shown, spring 15 is extended slightly clue to the weight of the empty car so that the contacts of interlock switch 43 are still closed. The position of axle 4 or the extension of springs 15 is indicative of the weight of car 11 or the load on car 11. Thus springs 15 constitute the resistant of a weighing device. Further extensionof spring 15, such as would be caused by a load on car 11, would move leaf spring 44 away from switch 43 so that the latter would open and interrupt the circuit to push buttons 57 and 58 whereby the elevator could be operated only by depressing buttons 55 or 56. In this released position solenoid 25 is not energized and link 21 does not engage arm 18. Accordingly, if car 11 is loaded and axle 4 swings about pins 7 to extend spring 15 commensurate with the total load or tension in tow line 10, link 21 is not affected. Assuming now that push button 55 is depressed, a circuit is closed from line 50 through line 74, safety switches 30, 41 and 42, the central bus bar of bus 54, brush 82, lead 84, push button 55, wire 85, brush 81, the upper bus bar, lead 87, limit switch 60, solenoid coil 52, and lead to cause energization of solenoid 52 which pulls switch 69 to the left and switch 63 to the right to energize motor 14 turning drum 12 so that car 11 ascends. Push button 55 has to be held closed while the car is in motion. At the same time that motor 14 is energized, solenoid 25 is also energized through leads 72 and 73, pulling link 21 into groove 20 so that this clutch is engaged and link 21 is actuated longitudinally if axle 4 changes its position. After link 21 has been lifted by solenoid 25 the latch member 46 engages catch 48 so that the clutch which consists of link 21 and groove 20 is locked in the engaged position. However, it is locked only if springs 15 have yielded to a load on car 11. It would not be desirable to cause the car to stop in response to the slightest movement of axle 4 as would occur due to acceleration forces or certain movements of the passenger riding on car 11, therefore, a clearance between link 21 and safety switch 30 or lever 32 is provided permitting certain excursions of axle 4 without opening switch 30. However, if the tension in tow line 10 is increased a certain amount, for instance if a person steps on the car while the latter is in motion, or an obstacle is placed in the path of the car, link 21 is pushed against lever 32 as shown in Fig. 6 to open switch 30 and stop the car by interrupting the circuit. Motor 14 is provided with an electrically released brake so that it stops quickly after the current is shut 011. Since brake motors for elevators are conventional, the brake release solenoid, which is usually connected in parallel with the motor leads to be energized simultaneously with the motor, has not been shown specially in the electric diagram but is considered included in motor 14. If during the ascent of the elevator car the load becomes lightened, as for instance if the passenger steps off the car, link 21 is pulled upwardly due to contraction of springs 15 so that after the play is taken up, hook 34 is lifted by groove 33 to actuate lever 32 which in turn opens switch 30, as illustrated in Fig. 7. The pull of solenoid 25 is very light since very little force is required to operate safety switch 30, so that the resistance oifered by the friction clutch to the movement of axle 4 due to overtravel after operation of switch 30 is negligible. After the motor is stopped and solenoid 25 denergized, the clutch remains engaged due to latch 46 until the load is removed from car 11 and axle 4 returns to the position shown in Fig. 1 where stop 49 trips latch 46 to release link 21 from groove 20. In case of slack ening of the tow line 10 springs 15 have sufficient force to pull axle 4 toward the stop on bracket 17, whereby arm 45 opens switch 41. Spring27 is subordinate in strength to the holding force of the clutch so that when axle 4 swings in a counterclockwise direction while solenoid 25 is energized the friction of the clutch is ample to push link 21 downwardly to bend spring 27 and open switch 30. When the elevator is unloaded and at rest and solenoid 25 deenergized, the load on the elevator can be varied without affecting link 21, as the latter is disengaged from arm 18. If the load placed on the elevator car is above the permissible maximum, springs 15 are fully extended and arm 18 abuts against bracket 40, in which position lead spring 44 holds safety switch 42 open so that the elevator cannot be started. The safety device thus makes it necessary that the entire load is placed on the elevator car before it is started. If an additional load is added after the start, the elevator is stopped. This is also true when the elevator car descends. If an obstacle or resistance is placed into the path of the elevator car during the descent the tension in tow line is decreased, resulting in a contraction of springs and clockwise movement of axle 4 about pins 7 to pull link 21 upwardly and actuate lever 32 through links 22 and book 34, thereby opening switch 30.

Having thus described my invention, I claim:

1. In an elevator having a movable car, a tow line to suspend said car, a motor to drive said car, and control means to energize said motor and stop said car, in combination, a safety device including an element carrying a sheave engaged by said tow line, said element being movable and urged to move in one direction due to the stress in said tow line, resilient means connected to resist the movement of said element in said one direction and to urge said element to move in the opposite direction, said resilient means being of a nature to ofier increasing resistance as said movement in said one direction is increased, and means responsive to the movement of said element in either direction due to a variation of the load after start of operation relative to the load at the start of the operation to urge said control means to deenergize said motor and stop said car, said means responsive to the movement of said element being adapted to be operable only when said motor is energized.

2. The construction as claimed in claim 1 where said means responsive to the movement of said element in cludes a mechanism engageable with said element and operatively connected with said control means to deenergize said motor and to stop said car, and means energized simultaneously with said motor to engage said mechanism with said element while said motor is energized, whereby movement of said element while said car is moving operates said control means to deenergize said motor and to stop said car.

3. The construction as claimed in claim 2, and means to bias said mechanism into a neutral position where said mechanism is disengaged from said element and not affecting said control means.

4. The construction as claimed in claim 2, where said control means includes an electric circuit having manually operable means for closing said circuit to cause energization of said motor and a safety switch to break said circuit and thereby deenergize said motor and stop said car, said mechanism being adapted to open said switch to break said circuit in response to movement of said element while said element is engaged with said mechamsm.

5. The construction as claimed in claim 4, and a second safety switch being operable to be opened by movement of said element to an extreme position in said opposite direction, to thereby deenergize said motor and stop said car.

6. The construction as claimed in claim 5, and a third safety switch to break said circuit, said third safety switch being operable to be opened by movement of said element to an extreme position in said one direction due to extreme tension in said tow line, to thereby deenergize said motor and stop said car.

7. The construction as claimed in claim 2, where said control means includes an electric circuit having first manually operable means located on said car and second manually operable means located remote from said car for closing said circuit to cause energization of said motor, an interlocking switch operatively connected with said element to render said second manually operable means inoperative in a position of said element responding to a tension in said tow line greater than the tension produced by the empty car.

8. The construction as claimed in claim 2, where said means energized simultaneously with said motor comprises an electrically operable solenoid.

9. The construction as claimed in claim 8, latching means operatively connected with said frictionally engageable mechanism to keep the latter in engagement with said element after said solenoid has been deenergized, and means to trip said latching means to disengage said frictionally engageable mechanism from said element.

10. The construction as claimed in claim 9, where said means to trip said latching means is dependent on the position of said element to trip said latching means when said elevator car is empty.

11. In an elevator having a movable car, a tow line to suspend said car, electrically driven power means to drive said car, and an electric control circuit which when closed causes energization of said power means, in combination, a safety device including a movable element, a pulley revolubly mounted on said element, said tow line passing over said pulley to transmit the tension in said tow line to said element to urge said element to move in one direction, spring means arranged to urge said element to move in an opposite direction, said spring means offering an increasing resistance to the movement of said element in said one direction as said element is moved in said one direction, whereby the position of said element is indicative of the tension in said tow line and the weight of said car, said electric control circuit including a normally closed safety switch in series with said circuit, a mechanism engageable with said element, said mechanism and part of said element together forming a friction clutch, and a solenoid energizable with said power means and operatively connected to engage said mechanism with said element, said mechanism being adapted to open said safety switch upon movement of said element while said solenoid is energized to open said circuit and deenergize said power means.

12. The construction as claimed in claim 11, and means operatively connected with said element to open said circuit when said element is in one of its extreme end positions to thereby deenergize said power means and to stop said car.

References Cited in the file of this patent UNITED STATES PATENTS 1,003,913 Kilcoyne Sept. 19, 1911 1,862,603 McNaught June 14, 1932 1,933,131 Wood Oct. 31, 1933 1,993,309 Rubin Mar. 5, 1935 2,619,195 wScott Nov. 25, 1952 2,644,546 Doolan July 7, 1953 2,674,347 Thompson Apr. 6, 1954 

